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Thread: Object of the Week February 6th 2022 - NGC 2242

  1. #1
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    Object of the Week February 6th 2022 - NGC 2242

    NGC 2242

    Other Names PN G170.3+15.8

    Planetary Nebula

    Constellation Auriga

    RA: 06h 34.127m

    Dec: +44° 46.62'

    Mag: 15.1 (P)

    Size: 22.0"

    Mag C. Star: 17.6

    When we think of planetary nebulae in Auriga we tend to think of IC 2149 but many observers are
    unaware of the fact that there is also an NGC planetary in the constellation. When Lewis Swift
    discovered NGC 2242 in 1886 using the 16” refractor at the Warner observatory in Rochester,
    New York he could not have realised that he had found the last planetary nebula to be added
    into the NGC. Having said that for most of the time since its discovery NGC 2242 has been
    thought to be a galaxy, and indeed Zwicky catalogued it as such in the CGCG. it was not until
    1987 that it was examined and found to be a planetary nebula, albeit a rather faint one, although
    Sulentic and Tifft had suggested it might be a PN in 1973 in the RNGC.

    ngc2242_OOTW2.jpg

    The planetary is thought to be about 6500 light years away and about 1500 light years above
    the galactic plane. It is probably one of only a handful of halo PN known. In age terms
    NGC 2242 is thought to be very old. The morphology of the planetary is somewhat
    reminiscent of the much brighter NGC 7662 with an inner ring and halo, at least on the
    SDSS image.

    ngc2242_sdss.jpg

    The central star is very hot with a modelled temperature of around
    137000K so most of its light output will be in the UV. Its spectral type is given as
    O(H). This has translated to a very high nebular temperature of perhaps 25000K.
    NGC 2242’s late re-classification as a planetary nebula is probably why it has not
    appeared in any of the main observing guides. There also appears to be some confusion
    over how best to observe it. Steve Gottlieb suggested that when using his 17.5” it did
    not respond well to filters however, Kent Wallace in his monumental guide on visual
    observations of planetary nebulae using a 20” (50cm) suggests that it does respond
    to both UHC and OIII filters so it maybe that you need a larger telescope to get a filter
    effect. There are no reports that it responds to an H-Beta filter. Its spectra shows quite
    strong OIII and H-beta lines so it should really respond to those filters. NGC 2242 is
    probably one of the faintest, if not the faintest, planetary nebulae in the NGC so it may
    require significant apertures to find, possibly in the range 40 cm at up. Swift described
    the object at discovery as exceedingly faint and very small and round. I suspect that to
    see much more than a faint circular patch is going to require a telescope in the 50cm+
    class and probably better skies than we have in the UK. I suspect that because of its
    size that a high power is probably going to be required to find it, which may also be part
    of the reasons that filters do not work so well. The central star is going to be much too faint
    to see at around 18th magnitude. The Interstellarum Field Guide suggests that it is an
    object for larger telescopes although I guess that observers from high altitude may see
    it with smaller ones.

    NGC2242_with_x4_insert.png

    Image of NGC 2242 by Ian Smith

    And as always,
    Give it a go and let us know! Good luck and great viewing!
    22" Obsession UC
    15" Obsession UC
    Takahashi Mewlon 210
    TMB 130 LW

  2. #2
    Member Raul Leon's Avatar
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    Hi here's my observation from 11/9/2012: ngc 2242 planetary nebula in Auriga ; mag:15 ; size:22" ; small, extremely faint round glow; observed with hood and UHC filter; one of the dimmest objects I've observed! I used a 6mm Ethos at 304x with my 14.5 Starstructure f/4.3ngc 2242.jpg
    Raul Leon
    14.5 Starstructure Dobsonian f/4.3

    http://thestarsketcher.blogspot.com/

  3. #3
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    My notes with my 12" dob read that I am unsure if I saw it. At 88x and 188x using an OIII filter I suspect a faint small glow around a faint star. I also noted that I need to revisit this nebula with my 20" which is going to be hard since that telescope now is in Chile and the nebula doesn't rise high above the horizon there...

  4. #4
    Member Clear Skies's Avatar
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    Two observations in my log for this little round glow, because that's what is was, both in the autumn of 2017 and the winter of 2020, both from the French Ardennes and both in my 14" SCT. The highest magnification I used was 259x, but it remained even in brightness. A UHC filter did not enhance the view and the first time around it vanished when I used an OIII filter.

    Perhaps other observations in larger apertures teased out its annular nature?

    NGC2242-1.jpg NGC2242_2.jpg NGC2242-3.jpg

    Click here to download the observing guide.
    Last edited by Clear Skies; February 6th, 2022 at 01:27 PM.
    Victor van Wulfen

    clearskies.eu | Clear Skies Observing Guides #CSOG | Blog | Observing Log | Observing Sessions

    - SQM is nothing. Transparency is everything.

  5. #5
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    Just checked my old entry with the former 20-inch under good transparency of a Pre-Alps location. I noted:

    faint, filled disk; small and nearly round, perhaps somewhat NE-SW elongated; does not respond well on [OIII] and Hß filters; CS steadily visible with averted vision; faint, small diffuse ring around central ring-like disk

    sketch: 20", 575x, NELM 6m5+, Seeing III
    NGC2242.jpg
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